Production of a hybrid capacitive storage device via hydrogen gas and carbon electrodes coupling

Conventional electric double-layer capacitors are energy storage devices with a high specific power and extended cycle life. However, the low energy content of this class of devices acts as a stumbling block to widespread adoption in the energy storage field. To circumvent the low-energy drawback of electric double-layer capacitors, here we report the assembly and testing of a hybrid device called electrocatalytic hydrogen gas capacitor containing a hydrogen gas negative electrode and a carbon-based positive electrode. This device operates using pH-universal aqueous electrolyte solutions (i.e., from 0 to 14) in a wide temperature range (i.e., from − 70 °C to 60 °C). In particular, we report specific energy and power of 45 Wh kg −1 and 458 W kg −1 (both values based on the electrodes’ active materials mass), respectively, at 1 A g −1 and 25 °C with 9 M H 3 PO 4 electrolyte solution. The device also enables capacitance retention of 85% (final capacitance of about 114 F g −1 ) after 100,000 cycles at 10 A g −1 and 25 °C with 1 M phosphate buffer electrolyte solution. Conventional electric double-layer capacitors show limited energy content for energy storage applications. Here, the authors report an electrocatalytic hydrogen gas capacitor with improved specific energy, which can operate in pH-universal aqueous electrolyte solutions and a wide temperature range.